The applicants propose to sequence the chromosomal region corresponding to the retinoblastoma susceptibility locus. The DNA segment spans almost 200,000 bp within the q14 band of human chromosome 13. The applicants will use established sequencing methods to sequence cloned fragments of the gene. They will also apply several alternative sequencing approaches that they have developed as shortcuts to conventional techniques or where previous methods are inadequate. In addition, they will explore powerful yet inexpensive new computer methods for storing, handling, and analyzing the large amount of sequence data to be generated in projects of this kind. The complete genomic sequence of the retinoblastoma susceptibility locus will greatly facilitate various current and future investigations by the project laboratory and other laboratories into the nature of mutations of the gene that lead to malignancy. Such subsequent studies will allow a better understanding of the domains of the genetic locus, and the encoded protein, that are essential for its normal tumor-preventing function. Also, knowledge of the complete sequence of the retinoblastoma gene will simplify the detection of mutations of the gene in patients with retinoblastoma, thereby improving the genetic counseling of those patients and their relatives. Finally, in view of the debate about sequencing the entire human genome, this project may serve as a pilot project to test the practicality and cost-effectiveness of having small research teams sequence and analyze large stretches of human DNA.